This invention is in the field of infra-red communications. More particularly, it relates to multi-user infra-red communication systems.
Methods and apparatus for emitting infra-red signals for use in wireless communication systems are known. One such system is shown in U.S. Pat. No. 4,628,541, the specification of which is incorporated herein for all purposes. Known infra-red wireless keyboard systems can accommodate multiple users with multiple channels. In operation, an ID code is combined with the signals transmitted by the wireless keyboard. This combined signal is then transmitted at a particular carrier frequency. The receiver, which is coupled to the computer system, can determine from the received ID code which channel the keyboard is using. Although this arrangement allows for multiple users, these multiple users cannot simultaneously access the computer without causing mutual interference. If two users were to attempt to input data simultaneously into their respective computer systems, the fact that the carrier frequencies are the same will result in the loss of the ID code and data to both systems.
As an example of the interference problem, assume two different users are transmitting to two separate computer systems, the first user transmitting on channel 1 and the second user transmitting on channel 2. Using known wireless keyboard systems, the first user can transmit data to the first computer system through channel 1, but if the second user attempts to transmit data simultaneously to the second system, both sets of data will be destroyed due to interference.
Given the limitations of the known wireless keyboard systems, a wireless keyboard that can transmit data simultaneously with other keyboards without interfering with them or being interfered with would be an advance of the known art.